[ubuntu] Net freeze while Repo Synchonizate

Hey guys,

i m having porblem with internet connection. When i start synchonizing repository (Github) it usually stops at 30 - 40 % and starts showing this error:

When this error shows, my computer stops receiving any data from the internet. Also i´m not able to visit any website by webbrowser (Chromium). It looks like i´m not connected to the internet. i´m connected by cable.

If i stop synchonizing after few seconds the internet starts working again.

Does anybody have an idea what is wrong with it?

Thanks in advance.